In semiconductor technologies, image sensors are used for sensing a volume of exposed light projected towards the semiconductor substrate. Complementary metal-oxide-semiconductor (CMOS) image sensor devices are widely used in various applications such as digital still camera (DSC) applications. These devices utilize an array of active pixels or image sensor cells, including photodiode elements and MOS transistors, to collect photo energy to convert images to streams of digital data. However, image sensor devices suffer from electrical cross-talk.
For example, consider optical applications such as DSC, which require high-performance imaging with low electrical cross-talk, low noise, and superior optical performance. An image sensor including photodiodes and MOS transistors can be used in these applications. The photodiodes and MOS transistors can be formed in a P− silicon semiconductor layer disposed on a P+ silicon substrate, and an incident light generates electron-hole pairs in the P− silicon layer. The generated electrons outside depletion region will diffuse into neighboring photodiode and causes electrical cross-talk. The electrical cross-talk will degrade spatial resolution, reduce overall optical sensitivity and result in poor color separation. The electrical signal of light targeted for one image sensor element also may spread to other image sensors, which causes crosstalk. Improvements of the image sensor and/or the corresponding substrate are desired.